1. Field of the Invention
Aspects of the present invention relate to an additive to electrodes for a fuel cell, an electrode for a fuel cell including the same, a method of manufacturing the electrode for a fuel cell, and a fuel cell using the electrode. More particularly, aspects of the present invention relate to an additive demonstrating improved phosphoric acid retention capacity, high temperature stability, and proton conductivity, as well as an electrode for a fuel cell including the additive, a method of manufacturing the electrode for a fuel cell, and a fuel cell using the electrode.
2. Description of the Related Art
Proton conductors that have excellent proton conductivity at a temperature in the range of 100-300° C. and are stable during long-term use in that temperature range are required in a fuel cell for power generation efficiency, system efficiency, and long-term durability of the components.
In a solid polymer electrolyte membrane fuel cell that uses phosphoric acid as a proton conductor, a sufficient amount of phosphoric acid needs to be supplied as a proton conducting medium for the high proton conductivity needed to promote the electrochemical reactions occurring in the electrodes. For this purpose, an additional process of doping with phosphoric acid is needed.
The added phosphoric acid flows within the electrode or is transferred through the electrolyte during the operation of the fuel cell, and flows from the fuel cell along with the water that is generated.
However, the phosphoric acid forms polyphosphoric acid at a fuel cell operating temperature in the range of 150-300° C. At this high temperature range, the generated polyphosphoric acid lowers the chemical stability of the electrolyte membrane. Thus, gaseous reactants may permeate through the electrolyte membrane and the open circuit voltage of the fuel cell may be reduced. As a result, the efficiency of the fuel cell may decrease.
A method of preparing an electrode material using an amine as a polymer forming precursor is disclosed in U.S. Patent Application Publication No. 2006-0033226.